| PM2.5（fine particulate matter）pollution is the main air pollution problem in our country.With the gradual control of industrial pollutants such as SO2 and NOX,NH3,as an air pollutant mainly emitted from agricultural sources,plays a key role in the formation of PM2.5.There is an urgent need to study the control and emission reduction strategies of atmospheric ammonia.Therefore,this paper,based on the meteorological model WRF and the air quality model CMAQ,simulates the impact of different ammonia emission reduction scenarios on PM2.5 and its inorganic salts in2017,and focuses on analyzing the effect of national ammonia emission reduction measures on PM2.5 concentration in YRD.First of all,the accuracy of the model is verified.The temperature and wind speed are verified by the WRF model,and it is found that the simulated values are in good agreement with the observed values.The CMAQ model is used to verify the PM2.5 simulated data of the outer grids of 13 cities including Hangzhou,and the results meet the"deviation standard"of the secondary index.The simulation data of the inner grid of the three cities of Hangzhou,Shanghai,and Nanjing are verified,and the simulation effect has been improved to a certain extent.Overall,the WRF-CMAQ model simulation results meet the accuracy requirements.Secondly,the effect of ammonia emission on PM2.5 concentration is simulated.It is found that ammonia emission reduction in the atmosphere can generally reduce PM2.5 concentration by 3～25μg/m3 in January;the PM2.5 concentration generally decreases by 2～20μg/m3 in April and October;the PM2.5 concentration decreases below 10μg/m3 in July.The result shows that ammonia emission reduction has the greatest impact on ammonium salt,followed by nitrate,and the least impact on sulfate.Then,using the IPR method to analyze PM2.5,it is found that under the zero ammonia scenario,the EMIS is always the sourcing process of PM2.5,the CLDS and the DDEP are always the sinking processes of PM2.5.The processes affected by ammonia emission reduction are mainly the DDEP,the VDIF and the AERO.It reduces the influence of the ZADV in April and October,so that PM2.5 concentration drops.And it reduces the effect of the HADV on PM2.5 elimination as well.So it comprehensively affects the PM2.5 concentration.Except in January,ammonia emission reduction also has a significant impact on the CLDS,which weakened the elimination effect.And the effect is the greatest in July.In addition,through the daily analysis of the PM2.5generation process,it is found that the generation rate of each generation process rate and the effect of ammonia emission reduction is smaller in the daytime,and is larger at night,showing a"vase"shape,with the most significant in April and July.At last,in the impact of ammonia emissions on PM2.5 and its inorganic salts in YRD,it is found that the most important impact is ammonia emissions in internal regions,with a contribution rate of 80.47%.Among the external regions,Central China and North China have a greater impact,with contribution rates of 15.83%and 9.35%.Other areas have less impact due to geographical and topographical factors.The surrounding coordinated emission reduction has less impact on major cities but has a greater impact on other regions.Among the emission reduction measures taken,the overall coordinated emission reduction effect is better than the internal emission reduction.Considering the implementation difficulty and emission reduction effect of ammonia emission reduction measures,this paper recommends the proposed ammonia emission reduction degree is 50%. |
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